The invention relates to a method for fabricating drip irrigation pipes, or similar, comprising the following steps:    a) Extruding a plastic pipe through an extruding head;    b) Progressively reducing the pipe, from the diameter coming out of the extruding head to a final diameter which provides the extruded pipe with a conical shape for a certain initial length.    c) Inserting a plurality of dripping elements consecutively and keeping pace with the advance of the extruded pipe, through the extruding head and into the extruded pipe;    d) Advancing each dripping element to an area of the pipe, whereat each dripping element is brought to contact with a predetermined area of the inner surface of the pipe, while having a predetermined speed relative to the speed of the pipe when contact occurs;    e) Cooling the pipe with the dripping elements;    f) Perforating the pipe where the dripping elements are provided.
Some methods for fabricating drip irrigation pipes of the type described above are known from the state of the art.
All these methods aim at binding the dripping elements with a predetermined resistance, in order to prevent the detachment of the dripping elements. To  this end, substantially two methods have been developed. A first method provides that the dripping elements are deviated towards the pipe wall in the conical area, directly on exit from the extruding head and that, when the pipe and the emitting element are coupled, i.e. come to contact, the latter has a different speed, i.e. lower than that of the pipe. Further, downstream from the contact area, generally in a so-called subsequent calibrator, or even in the contact area itself, there are provided means for compressing the dripping elements against, the pipe. Obviously, once the contact has occurred, the speeds of the pipe and of the dripping elements are the same.
This method is disclosed for example in document U.S. Pat. No. 5,271,786. In this method, the dripper units are displaced on a guide which is provided coaxially inside the extruded conduit. The contact between the dripper unit and the internal surface of the conduit takes place in the region of a first step of reduction of the cross-section of the extruded conduit. In this document the dripper unit is displaced transversally in the direction of the conduit by means of a guide section which is inclined in a direction converging against the conduit wall. At the location of contact of the dripper unit with the conduit, the conduit wall being reduced to a lower diameter has a substantially conical orientation and converges against the inner guide for the dripper unit. In this situation the leading end of the dripper unit is raised against the conically reducing wall of the extruded conduit and hurts it with  a leading corner. This may lead to damage of the softened wall of the conduit.
A second method provides that the dripping elements are brought to contact with the pipe in an area in which the diameter of the latter has been reduced, that is downstream from the conical narrowed length. In this case, the emitting elements are advanced, at least in the area or location whereat they contact the pipe, at a speed which is substantially identical to that of the pipe itself. Once again, the contact is followed by a compression step. This method is disclosed in documents EP 344 605 and EP 872 172.
In both this documents, the orientation of the contact surfaces of the extruded conduit and of the dripper unit are convergent and such that the first contact takes place between the region of the corner of the leading head of the dripper and the inner surface of the extruded conduit.
In the first method, in order that the dripping elements are well fastened to the pipe, either long compression areas or considerable compression forces have to be provided. However, these dimensioning provisions are subject to substantial restrictions, due to the fact that the pipe must not be prevented from axially sliding, so that the correct formation of the pipe is not jeopardized. On the other hand, the second method requires a sufficiently accurate adjustment of the feed speed of the pipe and of the emitting elements, in order to ensure that the speeds of these two parts upon contact therebetween are substantially  the same. Also in this case, the path along which the pipe and the dripping elements are submitted to mutual compression must be sufficiently long, or the compression force must be sufficiently high, therefore involving the risk that the advance of the extruded pipe is obstructed or hindered.
In all the disclosed methods and devices, care is taken to the fact that at the moment of the contact between extruded conduit and dripper unit both have either the same speed or the dripper unit is at rest or has a lower speed than the conduit.
Furthermore after the first contact, the dripper unit is not any more pushed or drawn by dedicated means, but is dragged by the extruded conduit itself.
Both the above measures are intended to avoid the damaging of the conduit during the contact between dripper units and conduit and during welding of the dripper units to the conduit.